Heavy equipment, such as large earthmoving vehicles, can use a retarder to supplement the braking provided by conventional brakes. Retarder operation is based on a manual setting and is either on or off. Some types of retarder have various level settings. When on, the retarder is active in all driving conditions including slowing to a stop by downshifting through low gears. In this, and some other conditions, the retarder may cause a rough downshift, which at a minimum is uncomfortable for the operator and at worst, may cause undue wear on drivetrain components.
U.S. Patent Publication No. 20110125376 (“the '376 publication”) describes an automatic downhill speed control system in a machine. The published application describes a retarder control for slowing the machine. The retarder can be set to an automatic position. When the retarder is in the automatic mode, the controller will determine the grade of path. Based on the grade and the vehicle speed, the gear will be changed automatically as per a predetermined gear selection sequence. When the vehicle is moving on the flat ground the automatic control is deactivated. The '376 publication fails to disclose automatically disengaging or changing the retarding level based on an analysis of the speed, grade, and/or impending gear change.